Project Summary/Abstract Suicide rates have nearly doubled among adolescent girls over the past decade. During this same time period, social media sites (e.g., Instagram, Snapchat, Facebook) have become ubiquitous, with nearly 97% of youth now using social media. Social media offers both risks and benefits for adolescent development. However, there is likely a vulnerable subset of youth for whom social media use influences suicidal thoughts and behaviors (STBs). The primary goal of this study is to examine how and for whom social media use contributes risk for STBs, so that we may better identify and intervene with youth most at risk. A multi-method approach, integrating computational psychiatry and experimental techniques, will be used to investigate the specific mechanisms by which social media use affects STBs. Data will be collected from both an existing dataset (n ~ 2,000) and a recruited sample (n = 90 adolescent females, ages 14-17, with lifetime history of STBs). To identify specific, directly observable social media experiences that heighten risk for STBs, digital trace data (i.e., social media content and meta-data) will be collected directly from adolescents? social media pages and analyzed using machine learning techniques. In addition, an innovative laboratory paradigm with eye- tracking/pupillometry will be used to examine cognitive and affective responses to social media use that increase vulnerability to STBs. Participant STBs will be assessed at baseline, 3-month-, and 6-month follow ups. The aims of the study are well-aligned with the candidate?s long-term career goal of becoming an independent investigator of adolescent social media use and mental health. To purse this research agenda going forward, the candidate proposes training in four key areas: (1) machine learning methods for analyzing digital trace data, (2) experimental eye tracking/pupillometry paradigms, (3) mechanism-based translational research in adolescent suicide risk, and (4) professional development, with an emphasis on training in effective interdisciplinary collaboration and the ethics of social media research. A team of mentors and consultants from multiple disciplines will facilitate the candidate?s training, including experts in youth suicide risk, machine learning and natural language processing, and experimental peer interaction paradigms. The diverse resources available at Brown University and Rhode Island Hospital will ensure successful completion of the project and foster the development of the candidate?s research program. The proposed study has the potential to contribute significantly to our understanding of the role of social media in adolescent suicide risk. Completion of the proposed research and training goals will uniquely position the candidate to become a leader in the field of adolescent social media use.